pyrolusite

Pyrolusite is a mineral form of manganese dioxide (MnO2). It is black to bluish-black, with a metallic to earthy luster and a black streak. It crystallizes in the tetragonal system and commonly occurs as tabular or prismatic crystals, as well as botryoidal, nodular, or columnar masses. It is the most common natural oxide of manganese.

Pyrolusite forms in oxidizing environments of manganese-rich ore deposits and in hydrothermal veins; it occurs as a secondary mineral after weathering of other manganese minerals. It is frequently found together with other manganese oxides such as manganite, psilomelane, and cryptomelane.

Physically, pyrolusite has a Mohs hardness of about 6 to 6.5 and a specific gravity of about 4.9 to 5. It is opaque and has a blue-gray to black streak. The color is typically black to steel-gray and becomes more metallic in fresh surfaces.

Economically, pyrolusite is the principal source of manganese, a metal essential for steel production and various chemical applications. Manganese dioxide obtained from pyrolusite is used as a depolarizer in dry-cell batteries, as a catalyst, and in chemistry to prepare other manganese compounds such as potassium permanganate. It is also used as a black pigment (Mars Black) in paints and ceramics, and in glassmaking.

Mining and processing involve ore concentration and subsequent reduction to produce metal manganese or MnO2 for industrial uses.

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